Adjustable electrode arrangement for capacitance plethysmography



United States Patent [72] Inventor Stepan Fill! 2,099,938 1 1/1937 Lockhart 128/105 Prague, Cuchoslova 2,667,159 1/1954 Goldberg et a1. l28/2.05 [21] Appl. No. 710,585 2,827,600 3/1958 Mullikin 317/249X [22] Filed March 5, 1968 3,090,377 5/1963 Salisbury et l28/2.05 [45] Patented D. 8, 1970 3,361,129 1/1968 Figar 128/105 [73] Assign Cakmvmh akademic ved Primary Examiner- Richard A Gaudet Cmmovakh Assistant Examiner Kyle L. Howell Anorney- Richard Low [54] ADJUSTABLE ELECTRODE ARRANGEMENT F OR CAPACITANCE PLETI'IYSMOGRAPHY 8 Clllllll, Drawing F138.

128/21, 128/413 ABSTRACT: An electrode arrangement for taking plethysmo- Aflb 5/021 graphic capacitance measurements on a finger and'the like 1/40 having a supporting ring in which a flat spring metal strip is [50] Field of Search l28/2.l, coiled in a radial m to f a spiral whose ends overlap -1 -4 -P g 317/249, each other and are fastened to the ring by fastening assemblies 1 y) of which one can be shifted circumferentially on the ring and Rereienm cued the other radially. Abutments threaded on the ring for radial movement permit the shape of the spiral to be modified and UNITED STATES PATENTS are remotely operated by tubular handles of insulating materi- 1,551,661 9/1925 Hill 317/249 al.

l ADJUSTABLE ELECTRODE ARRANGEMENT FOR CAPACITANCE PLETI-IYSMOGRAPHY BACKGROUND OF THE INVENTION This invention'relates to plethysmograph y, and particularly to an adjustable electrodearrangement for measuring volume changes in afinger or like elongated body portion by sensing the capacitance between the finger and an electrode.

It has been found that valuable 'data can be derived from information on volume changes in one or more short longitudinal sections of a finger. The electrode assembliesnow available-provide only information on volume changes over the entire length or a major portion of the length of a finger. Such electrode assemblies, however, do not give a possibility of adjusting their shape precisely to the body surface under investigation and consequently the measurements materialized by them cannot be precise enough;

The object of the invention is the provision of an electrode assembly which permits capacitance measurements to be taken with great precision on a very short section of a human finger or like body parts of a man or animal. Several such electrode assemblies when used combined together provide a.

more precise information on volume and volume changes over the entire length or a major portion of the length of theorgan under investigation.

SUMMARY or THE lNVENTlON In one of its aspects, the invention resides mainly in an electrode arrangement in which an elongated electrode member of flexible, electrically conductive material is fastened by its two ends to a support in a position in which the electrode member extends'about an' axis in a radial plane to form a spiral, the two ends bein'g radially offset in the plane. The fasteningv meanswhich fastens one end of the electrode l member to the support is provided withsecuring means per mitting the fastening means to be secured .to the support in a plurality of positions circumferentially offset relative tothe axis.

Other features, additional objects, and many of the attendant advantages of this invention will readily be appreciated as the same becomes better understood by reference to the following detailed description of a preferred embodiment when considered in connection'with the accompanying drawing.

BRIEF DESCRIPTION or THE DRAWING In the drawing which is on a scale of approximately 2:1, FIG. 1 shows an electrode arrangement of the invention in front elevation andpartly in section; and

FIG. 2 shows the device of FIG. 1 in side-elevational section on the line lI-Il.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing in detail, there is seen a sup-.

the two longitudinal ends ll, 12 of the strip are radially offr set in the common plane.

The end 11 is fastened to the ring by a pin,41 which passes radially outward through a circumferentially elongated slot 21 in the ring. Theouter end of thepin carries a knurled knob 40 provided with corrugations 44 whose projections and recesses are held in engagement with corresponding corrugations 28 of the ring 20 along the slot 21 by a resilient collar 45 between the enlarged inner end 42 of the pin 41 and the inner wall of the ring 20, the end 11 of the strip 10 being fixedly fastened to the innerend -42by soldering ina manner not shown. 3

A portion of the strip 10 intermediatethe ends l1, 12 is received with ample clearance in a circumferential passage in the enlarged inner end portion 30 'of a fastening pin 34 radially slidable in a bore of thering 20 and secured against rotation by a key or spline 33. The second end l2tof the strip 10 is attached to the end portion 30 of the pin 34.

The outer end portion 31 of thepin 34 is threaded and carries a knurled nut 32 secured against radial movement by a flange 23 fixed on the outer circumference of the ring 20 which engages an annular groove in the nut 32. When the nut is turned, the pin 34 moves the-end lzof the metal strip 10 toward and away from the axisof the ring 20.

The other end 11 may be shifted circumferentially by pulling the knob 40 in a radially outward direction against the resilient restraint of the collar 45 until the serrations 44 clear the serrations 28 whereupon the pin 41 may be moved in the slot 21. Even when the spiral of the strip I0 is tightened as far as the slot 2] permits, the inner diameter of the spiral is still several times the axial width of the strip 10, and approximately three times that width in the illustrated embodiment.

The spiral shape of the strip 10 may be modified by threaded abutment spindles 26 of whichonly one is shown in the drawing. The spindles may be inserted as needed into internally threaded radialopenings 22 in the ring 20 which are distributed over the circumference of the latter. Each spindle 26 is radially shifted by a means of alilexible plastic tube 27 slipped in tight engagement over the radially outer end of the spindle 26, thereby permitting the spindle to be turned from a remote location without interference of the operators body with the capacitance measurements taken.

As is indicated in FIG. 2 in broken lines, additional rings 20', 20f equipped in the same manneras the, ring 20 may be mounted in axial alignment on the base 25 for takingsimultaneous capacitance readings on sequential longitudinal portions of a finger whose tip is supported on a plate 29.

The electricalcircuit in which the metal strip 10 forms hot plate or electrode of a capacitor using ambient air as the dielectric and the tested finger as the other plate has not been shown since it may be entirely conventional and is not directly relevant to this invention. Insulating material employed for insulating the electrode 10 from ground has not been specifically indicated in the drawing. It is normally adequate to attach thelzero potential of a capacitance bridge to the ring 20 which is nonconductively.connected to the electrode 10 by the pins 34, 41 and the spindles 26. The ring 20 is made of metal and grounded thus formingscreening of the spiral 10. The tested finger is also grounded. The insulating lacquer provided at least on the radially inner major face of the strip 10 prevents a short circuit in the measuring circuit if the tested finger should touch the strip 10.

The arrangement illustrated permits the electrode strip 10 to. be adjusted for a small clearance between the strip and the circumference of a narrow longitudinal zone of the tested finger, thereby improving the sensitivity of the plethysmographic equipment. If several electrode arrangements are axially juxtaposed as indicated in FIG. 2, the electrode of each may be adjusted to fit the different circumferential configurations of the several longitudinal finger portions respectively received therein.

While the invention has'been described with particular reference to a specific embodiment, it is to be understood that it is not limited thereto, but is to be construed broadly and restricted solely by the scope of the appended claims.

Iclaim: V

1. An electrode for use in an arrangement for measuring volume changes in a finger andthe like by capacitance plethysmography, comprising in combination:

a. a support; Y

b. an elongated electrode member of flexible, electrically conductive material;

.c. first and second fasten ing meansfastening the longitudinal ends ofsaid electrode member to said support in a position in whichsaid electrode member extends about an axis in a radial plane and forms a spiral defining a space adaptedto receive section of a finger or body part, the endslof said electrode member being radially offset insaid plane; i

d. securing means for securing said first fastening means to said support in a plurality of positions circumferentially offset relative to said axis;

e. wherein a portion of said support is annular about said axisand fo rmed' with a circurnferential slot therein, said first fastening means including a pin member attached to one 9f the ends of said electrode member and partly received in said slot for circumferential movement when released by'said securing means, the securing means including a clamping member movable on said pin member toward and away from a position of clamping engagement with annular portion.

2. An arrangement'assm forth in claim 1, wherein said second fastening include a fastening member attached to said annular portionaahd m the other end of said electrode member, said fastening. member being formed with a passage extending circurn-f'ere'ntially therethrough, a portion of said electrode member intermediate said ends thereof being received in saidpa sage.v r "3. An arrangement as set forth in claim 2, wherein said fastening member is elongated radially relative to said axis, an end portion of said fastening member adjacent said axis being formed said"passage,fand threaded means for radially moving said fastening member on said annular portion.

.nular portion is formed with at least one internally threaded opening radially therethrough, said abutment member being threadedly received in said opening, the arrangement further comprising an elongated operating member of electrically insulating material attached to said abutment member for turningthe same.

6. An arrangement as set forth in claim 1, wherein said electrode member is a flat strip having respective opposite faces directed radially toward said axis and towardsaid annular portion, at leastone of said faces carrying a coating of electrically insulating material.

7. An arrangement asset forth in claim 6, the width of said faces being much smaller than the inner diameter of said spiral. h

8. in an arrangement as set forth in claim 1, said clamping member and said annular portion being formed with radial projections and recesses conformingly engaged in said position of clamping engagement to prevent circumferential movement of said pin member, the arrangement further comprising yieldable resilient means biasing said clamping member toward the last mentioned position. 

